We propose the acquisition of a commercial turn-key Multispectral Optoacoustic Tomography (MSOT) system, specifically, the iThera MSOT inVision 256-TF. It will initially serve six NIH-funded research teams as Major Users to undertake biomedical research in conjunction with our NCI-designated Cancer Center (P30 CCSG). In addition, through the Southwestern Small Animal Imaging Resource (SW-SAIR) it will support six other current NIH funded research investigators and serve as a catalyst for new research. It is widely recognized that imaging enhances biomedical research, particularly in oncology, and cardiovascular disease. Tumors exhibit substantial heterogeneity, and thus, it is advantageous for each tumor to serve as its own control. Longitudinal studies in individual tumors enjoy three primary benefits: i) the need for fewer animals, ii) as a corollary, the need for less reagent (therefore, rare and costly drugs and antibodies can be screened more efficiently), iii) more robust statistics. Multispectral Optoacoustic Tomography appears particularly attractive for tumors growing in nude mice, since it provides both spatial anatomical resolution, as well as physiological attributes such as vascular oxygenation, and visualization of labeled reporter molecules. Whole mice may be observed in 8 minutes through a sequence of tomographic slices with 150 ?m in plane resolution. Ten wavelengths may be detected per second providing multispectral evaluation of specific chromophores. Significantly, appropriate choice of wavelengths provides direct sensitivity to oxy- versus deoxyhemoglobin concentrations, which may be additionally combined with specific fluorophore reporters. The MSOT inVision 256-TF offers multi tomographic slice imaging providing 3-dimensional representations. Of note this instrument if designed to be user friendly, allowing relatively simple implementation of measurements with straightforward analysis based on manufacturer's image processing algorithms. At the same time the MSOT inVision 256-TF provides a level of supplication to permit development of novel methods. UT Southwestern is well-endowed with diverse small animal imaging modalities including MRI, PET/CT, SPECT/CT, optical imaging and ultrasound, but we lack photoacoustic technology and believe this will provide unique additional capability. Optoacoustic imaging (photoacoustic tomography, in particular) is the most advanced hybrid modality at present. Hybrid modalities combine two of more modalities in a manner that gives the best imaging performance. In the MSOT system, the poor resolution of optical imaging is replaced by the high resolution of ultrasound tomography, while the high contrast of optical absorption is utilized in place of the rather low ultrasound contrast. Our Imaging Resource facilitates effective utilization of imaging modalities, optimized choice for specific biomedical questions, and the technical know-how to implement investigations. Advantages of this modality, and specific instrument, are presented for individual projects and more generally for the pre- clinical imaging resource.